Nagios

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Nagios

• Network Design and Operations24 July
  2009hervey_at_nsrc.org

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Introduction

• A key measurement tool for actively monitoring
  availability of devices and services.
• Possible the most used open source network
  monitoring software.
• Has a web interface.
• Uses CGIs written in C for faster response and
  scalability.
• Can support up to thousands of devices and
  services.

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Features

• Verification of availability is delegated to
  plugins
• The product's architecture is simple enough that
  writing new plugins is fairly easy in the
  language of your choice.
• There are many, many plugins available.
• Nagios uses parallel checking and forking.
• Version 3 of Nagions does this better.

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Features cont.

• Has intelligent checking capabilities. Attempts
  to distribute the server load of running Nagios
  (for larger sites) and the load placed on devices
  being checked.
• Configuration is done in simple, plain text
  files, but that can contain much detail and are
  based on templates.
• Nagios reads it's configuration from an entire
  directory. You decide how to define individual
  files.

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Yet More Features...

• Utilizes topology to determine dependencies.
• Nagios differentiates between what is down vs.
  what is not available. This way it avoids running
  unnecessary checks.
• Nagios allows you to define how you send
  notifications based on combinations of
• Contacts and lists of contacts
• Devices and groups of devices
• Services and groups of services
• Defined hours by persons or groups.
• The state of a service.

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And, even more...

• Service state
• When configuration a service you have the
  following notification options
• d DOWN The service is down (not available)
• u UNREACHABLE When the host is not visible
• r RECOVERY (OK) Host is coming back up
• f FLAPPING When a host first starts or stops or
  it's state is undetermined.
• n NONE Don't send any notifications

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Features, features, features

• Allows you to acknowledge an event.
• A user can add comments via the GUI
• You can define maintenance periods
• By device or a group of devices
• Maintains availability statistics.
• Can detect flapping and suppress additional
  notificaitons.
• Allows for multiple notification methods such as
  
• e-mail, pager, SMS, winpopup, audio, etc...
• Allows you to define notification levels.
  Critical feature.

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How Checks Work

• A node/host/device consists of one or more
  service checks (PING, HTTP, MYSQL, SSH, etc)?
• Periodically Nagios checks each service for each
  node and determines if state has changed. State
  changes are
• CRITICAL
• WARNING
• UNKNOWN
• For each state change you can assign
• Notification options (as mentioned before)
• Event handlers

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How Checks Work

• Parameters
• Normal checking interval
• Re-check interval
• Maximum number of checks.
• Period for each check
• Node checks only happen when on services respond
  (assuming you've configured this).
• A node can be
• DOWN
• UNREACHABLE

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How Checks Work

• In this manner it can take some time before a
  host change's its state to down as Nagios first
  does a service check and then a node check.
• By default Nagios does a node check 3 times
  before it will change the nodes state to down.
• You can, of course, change all this.

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The Concept of Parents

• Nodes can have parents.
• For example, the parent of a PC connected to a
  switch would be the switch.
• This allows us to specify the network
  dependencies that exist between machines,
  switches, routers, etc.
• This avoids having Nagios send alarms when a
  parent does not respond.
• A node can have multiple parents.

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The Idea of Network Viewpoint

• Where you locate your Nagios server will
  determine your point of view of the network.
• Nagios allows for parallel Nagios boxes that run
  at other locations on a network.
• Often it makes sense to place your Nagios server
  nearer the border of your network vs. in the core.

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Network Viewpoint
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Nagios Configuration Files
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Configuration Files

• Located in /etc/nagios3/
• Important files include
• cgi.cfg Controls the web interface
  and security options.
• commands.cfg The commands that Nagios
  uses for notifications.
• nagios.cfg Main configuration file.
• conf.d/ All other configuration goes here!

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Configuration Files

• Under conf.d/ (sample only)
• contacts_nagios3.cfg users and groups
• generic-host_nagios2.cfg default host template?
• generic-service_nagios2.cfg default service
  template
• hostgroups_nagios2.cfg groups of nodes
• services_nagios2.cfg what services to check
• timeperiods_nagios2.cfg when to check and
  who to notifiy

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Configuration Files

• Under conf.d some other possible configfiles
• host-gateway.cfg Default route definition
• extinfo.cfg Additional node information
• servicegroups.cfig Groups of nodes and services
• localhost.cfg Define the Nagios server itself
• pcs .cfg Sample definition of PCs (hosts)
• switches.cfg Definitions of switches (hosts)
• routers.cfg Definitions of routers (hosts)

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Plugin Configuration

• The Nagios package in Ubuntu comes with a bunch
  of pre-installed plugins
• apt.cfg breeze.cfg dhcp.cfg disk-smb.cfg
  disk.cfg dns.cfg dummy.cfg flexlm.cfg
  fping.cfg ftp.cfg games.cfg hppjd.cfg
  http.cfg ifstatus.cfg ldap.cfg load.cfg
  mail.cfg mrtg.cfg mysql.cfg netware.cfg
  news.cfg nt.cfg ntp.cfg pgsql.cfg
  ping.cfg procs.cfg radius.cfg real.cfg
  rpc-nfs.cfg snmp.cfg ssh.cfg tcp_udp.cfg
  telnet.cfg users.cfg vsz.cfg

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Main Configuration Details

• Global settings
• File /etc/nagios2/nagios.cfg
• Says where other configuration files are.
• General Nagios behavior
• For large installations you should tune the
  installation via this file.
• See Tunning Nagios for Maximum Performance
  http//nagios.sourceforge.net/docs/2_0/tuning.html

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CGI Configuration

• Archivo /etc/nagios3/cgi.cfg
• You can change the CGI directory if you wish
• Authentication and authorization for Nagios use.
• Activate authentication via Apache's .htpasswd
  mechanism, or using RADIUS or LDAP.
• Users can be assigned rights via the following
  variables
• authorized_for_system_information
• authorized_for_configuration_information
• authorized_for_system_commands
• authorized_for_all_services
• authorized_for_all_hosts
• authorized_for_all_service_commands
• authorized_for_all_host_commands

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Time Periods

• This defines the base periods that control
  checks, notifications, etc.
• Defaults 24 x 7
• Could adjust as needed, such as work week only.
• Could adjust a new time period for outside of
  regular hours, etc.

'24x7' define timeperiod
timeperiod_name 24x7 alias 24
Hours A Day, 7 Days A Week sunday
0000-2400 monday 0000-2400
tuesday 0000-2400
wednesday 0000-2400 thursday
0000-2400 friday
0000-2400 saturday 0000-2400

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Configuring Service/Host Checks

• Define how you are going to test a service.

'check-host-alive' command definition define
command command_name
check-host-alive command_line
USER1/check_ping -H HOSTADDRESS -w 2000.0,60
-c 5000.0,100 -p 1 -t 5
Located in /etc/nagios-plugins/config, then
adjust in /etc/nagios3/conf.d/services_nagios2.cfg
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Notification Commands

• Allows you to utilize any command you wish. We'll
  do this for our generating tickets in RT.

'notify-by-email' command definition define
command command_name notify-by-email
command_line /usr/bin/printf "b"
"Service SERVICEDESC\nHost HOSTNAME\nIn
HOSTALIAS\nAddress HOSTADDRESS\nState
SERVICESTATE\nInfo SERVICEOUTPUT\nDate
SHORTDATETIME" /bin/mail -s
'NOTIFICATIONTYPE HOSTNAME/SERVICEDESC is
SERVICESTATE' CONTACTEMAIL
From nagios_at_nms.localdomain To
grupo-redes_at_localdomain Subject Host DOWN alert
for switch1! Date Thu, 29 Jun 2006 151330
-0700 Host switch1 In Core_Switches State
DOWN Address 111.222.333.444 Date/Time
06-29-2006 151330 Info CRITICAL - Plugin timed
out after 6 seconds
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Nodes and Services Configuration

• Based on templates
• This saves lots of time avoiding repetition
• Similar to Object Oriented programming
• Create default templates with default parameters
  for a
• generic node
• generic service
• generic contact

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Generic Node Configuration
define host name
generic-host notifications_enabled
1 event_handler_enabled
1 flap_detection_enabled 1
process_perf_data 1
retain_status_information 1
retain_nonstatus_information 1
check_command
check-host-alive max_check_attempts
5 notification_interval
60 notification_period
24x7 notification_options
d,r contact_groups
nobody register
0
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Individual Node Configuration
define host use
generic-host host_name
switch1 alias
Core_switches address
192.168.1.2 parents
router1 contact_groups
switch_group
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Generic Service Configuration
define service name
generic-service
active_checks_enabled 1
passive_checks_enabled 1
parallelize_check 1
obsess_over_service 1
check_freshness 0
notifications_enabled 1
event_handler_enabled 1
flap_detection_enabled 1
process_perf_data 1
retain_status_information 1
retain_nonstatus_information 1
is_volatile 0
check_period 24x7
max_check_attempts 5
normal_check_interval 5
retry_check_interval 1
notification_interval 60
notification_period 24x7
notification_options c,r
register 0

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Individual Service Configuration
define service host_name
switch1 use
generic-service service_description
PING check_command
check-host-alive max_check_attempts
5 normal_check_interval 5
notification_options c,r,f
contact_groups switch-group
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Automation

• To maintain large configurations by hand becomes
  tiresome.
• It's better to simplify and automate using
  scripts.
• http//ns.uoregon.edu/cvicente/download/nagios-co
  nfig-scripts.tar.gz
• Or, export device (node) information from tools
  like Netdot, netdisco, OpenNMS, etc.

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Beeper/SMS Messages

• It's important to integrate Nagios with something
  available outside of work
• Problems occur after hours... (unfair, but true)
• A critical item to remember an SMS or message
  system should be independent from your network.
• You can utilize a modem and a telephone line
• Packages like sendpage or qpage can help.

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Some References

• http//www.nagios.org Nagios web site
• http//sourceforge.net/projects/nagiosplug
  Nagios plugins site
• Nagios. System and Network Monitoring by Wolfgang
  Barth. Good book onNagios
• http//www.nagiosexchange.org Unofficial Nagios
  plugin site
• http//www.debianhelp.co.uk/nagios.htm A Debian
  tutorial on Nagios
• http//www.nagios.com/ Commercial Nagios
  supportAnd, the O'Reilly book you received in
  class!

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Nagios Vista General (Tactical Overview)?

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• Pantalla de Status Detail

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Pantalla de Service Detail

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Tipos de Servicios

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Muestra de una Mapa de Estatus
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Vista General de Estatus (Status Overview)?
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Vista Sumaria de Hostgroups
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Historia o Tendencias de Hosts
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Histogram de un Host
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Event Logs
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Quien Recibe Notificationes